Coronary artery disease (CAD) affects almost 1.3 million Americans per year, making it the most common form of heart disease. CAD most often results from a condition known as atherosclerosis, which is the most common form of arteriosclerosis i.e. hardening of the arteries.
Atherosclerosis occurs when plaque forms inside the arteries. Plaque is made of cholesterol, fatty compounds, calcium and fibrin. As the plaque builds up, the artery narrows, making it more difficult for blood to flow through the arteries. When atherosclerosis occurs in a coronary artery, blood flow to the heart muscle is impeded. In time, the narrowed or blocked artery can lead to angina pectoris, Myocardial Infarct (MI) and possibly death. A similar processes can affect other arteries, such as the carotid, intra-cerebral, and renal arteries, as well as arteries of the upper and lower limbs, leading to stroke, renal failure, hypertension and malfunction of the limbs, depending on artery affected.
In order to reduce the risk of artery disease and its complications, one option is opening the artery narrowing induced by atherosclerosis, utilizing intra-lumen balloon inflation and/or intra-lumen stent deployment.
In balloon angioplasty, a guiding catheter is inserted through a small skin incision into an artery and advanced to the origin of the coronary artery. Next, a guide wire is advanced through the guiding catheter into the coronary artery and across the blockage site. Then, a long, thin catheter that has a small balloon on its tip (balloon catheter) is pushed over the guide wire. The balloon is inflated at the blockage site in the artery to flatten or compress the plaque against the artery wall, and is then deflated and withdrawn. Thus, the blockage is removed from at least a portion of the arterial lumen, and blood can flow more freely through the artery.
Another method for opening plaque blockage is stent deployment. A stent is a small mesh-like tube made of metal. The stent may be pre-crimped over a balloon on the tip of a balloon catheter and pushed over the guide wire (as explained above) to the blockage site, where it is then expanded and deployed by the pressure of the balloon inflation at the narrowed site, and as such, acts as a support or scaffold, keeping the vessel open. Stent procedures are usually used along with balloon angioplasty. The first balloon inflation prepares the narrowed site, and enables stent insertion and deployment by another balloon on which the stent is crimped on.
Alternatively, a self-expandable stent may be used, which does not require a balloon for deployment. Such stents are made of shape memory metal and are provided with a covering sheath that compresses the stent to a low profile prior to delivery to the deployment site. At the deployment site, the covering sheath is removed, and the shape memory metal enables the stent to regain its full diameter.
Such procedures may be used to open narrowing in arteries including coronary, carotid, intra-cranial, and renal arteries, and peripheral arteries in the legs and arms.
Unfortunately, these procedures pose a great risk to the patient as emboli, generated by the balloon inflation or stent deployment that crush the frail atherosclerotic plaque, or thrombotic material, may be released during them. Once released, these emboli have a high likelihood of getting lodged into the smaller vessels at a point of constriction downstream of their release point, causing the vessels to become occluded and preventing blood flow.
These adverse events may cause severe damage to the treated organ like myocardial infarction, stroke, renal failure or limb malfunction.
There are several known embolization protection devices based mainly on an additional small proximal or distal occluding balloon with some debris removal system, or a small filter attached to the guide wire with deployment and retrieval systems.
Examples of known embolization protection devices, include:
U.S. patent application Ser. Nos. 10/348,137, 11/387,366, 11/566,473 to Wholey et al;
U.S. patent application Ser. Nos. 11/763,118, 10/997,803 to Sachar et al;
U.S. patent application Ser. No. 11/271,653 to Blix et al;
U.S. patent application Ser. No. 09/952,375 to Fischell et al; and
U.S. patent application Ser. No. 09/845,162 to Wahr.
The above-mentioned devices have many limitations. The occluding balloon-based type induces ischemia since the occluding balloon stops the distal blood flow for a relatively long period. Moreover, the need for a special debris extraction catheter prolongs the procedure and increases its complexity.
The over-the-wire filter devices have a special guide wire with inferior crossing ability compared to the regular wires. The extra delivery sheath covers the filter prior to its deployment, increasing the wire profile, reducing its crossing ability and because of its larger size, may cause embolization. There is also difficulty delivering the filter to a proper site distally to the lesion and difficulty in maintaining its position during the procedure. The need for another retrieval system prolongs the whole procedure time.
It is no wonder that several clinical randomized studies showed that in a group of patients in which distal embolization protection devices were used, the overall adverse events were significantly higher than in the control group where such devices were not applied.
Therefore, there is a need for a new embolization protection device, which is an integral part of the intra-lumen device, which will decrease the risks of distal embolization during use of intra-lumen devices.
Trans Luminal Aortic Valve Implantation (TAVI) is a novel therapy which may be used as an alternative to standard surgical aortic valve replacement. The TAVI procedure is performed on the beating heart using catheterization methods without the need for a Sternotomy or a Cardiopulmonary Bypass. Currently, two devices are CE marked and the procedure may be performed via the transfemoral, or subclavian approaches in which the catheter carrying the valve is advanced retrogradlly into the aorta and the artificial valve is positioned at the native aortic valve annulus.
Another approach is the Transapical method which combines minimally invasive surgery and catheterization. The surgeon performs a small incision at the heart apex, through it, a catheter carrying the valve is advanced anterogradlly and the artificial valve is positioned at the native aortic valve annulus. This Anterograde method is also called PAVI (Percutaneous Aortic Valve Implantation). This new field of interventional cardiology is growing rapidly and there are many companies developing new TAVI/PAVI devices. One major drawback of this new technique is multiple emboli dislodgment from the artificial valve deployment site which is usually heavily calcified. Brain MRI studies showed some degree of emboli into the brain in as many as about 70% of the TAVI cases.